So am posting up the answer that helped @Ritu21
This is my actual workflow that does this:

The first two steps are self-explanatory. The query is just querying the same record set for 0 records, but I also put all the additional data onto the schema that came off the schema when I first loaded it. I think this is so the new List has the exact same structure as the old list. Make sure you put the targeting dimension on there too.

Then I just save the new list as the same name as the old list

Cheers
Darren